The traditional internal combustion engine relies on connecting rods for transmitting combustion power from a piston main body to a crankshaft of the engine, thereby converting the linear motion of the piston main body to rotational motion at the crankshaft. Combustion power is generated from the intermittent ignition of gasoline that is injected into the combustion chamber, which creates extreme pressures that are applied to the piston and connecting rod. In particular, the interface between the piston pin bore of the connecting rod and the piston pin experiences continuous radial loads during operation, where only a limited amount of a lubricant may be available for lubricating the interface. In an effort to enhance lubrication at the interface of the piston pin and the connecting rod bore, at least one lubrication recess may be provided along an inner surface of the piston pin bore.
Typically, the lubrication recess is created by machining an indentation into an inner surface of the piston pin bore of the connecting rod. The machining process may be a separate manufacturing operation that occurs after the connecting rod piston pin bore has been created through a material forming operation, such as, for example, forging. Machining operations may add to the expense and the complexity of manufacturing the connecting rod.
Accordingly, there is a need in the art for a connecting rod including a lubrication recess that is relatively cost-effective and simple to manufacture. Moreover, there is an ongoing need to streamline manufacturing processes associated with connecting rods while retaining strength and acceptable product life of connecting rod assemblies.